The stems of bioenergy sorghum and other C4 grasses represent more than 75% of plant shoot biomass when plants are harvested at the end of the season. The composition of stems affects the efficiency of conversion of stem biomass to biofuels, biopower, and its utility as a source of forage or feed for animals. Stem composition at harvest is therefore critically important for bioenergy crops. While grasses with various desirable properties have been selected, there remains a need in the art for producing varieties with improved starch accumulation in stems. Starch is a compact and energy dense polymer of hexose units derived from glucose, fructose and sucrose. Increased accumulation of starch in stems when stem sugar content reaches high levels could improve crop biomass yield by minimizing feedback inhibition of leaf photosynthesis and by increasing the capacity of stems to accumulate non structural carbohydrates (i.e., starch) and ‘sink’ strength. Efforts to identify sorghum lines exhibiting desirable stem composition have been complicated by the many factors which contribute to starch biosynthesis and breakdown, including the stage of plant development, signals from the photoperiod, temperature, and growing location. Without increased knowledge and availability of the regulatory elements driving expression of genes involved in starch biosynthesis or breakdown at various stages of plant development, it may not be practical to attempt to produce certain new genotypes of crop plants due to such challenges.